Insulating film and preparation method thereof, insulating composite film and preparation method thereof, and electrical equipment

Abstract

The embodiment of the invention provides an insulating film and a preparation method thereof, an insulating composite film and a preparation method thereof, and electrical equipment, and relates to the technical field of expansion materials. The insulating film comprises a fiber matrix and an expansion compound, and the expansion compound is compounded in the fiber matrix. The insulating film can be prevented from being separated or cracked, and the electrical property and the mechanical property of the insulating film are improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of expansion materials, and in particular to an insulating film and a preparation method thereof, an insulating composite film and a preparation method thereof, and electrical equipment. Background Art

[0002] Insulation paper is an important insulating material used in electrical equipment. It has good insulation properties, mechanical strength and heat resistance. It is widely used in various motors, transformers and other electrical equipment to ensure the safe and reliable operation of these equipment.

[0003] In related technologies, a certain thickness of expandable coating is typically applied to the surface of insulating paper to form an expandable insulating film. When used in motors, this expandable coating primarily secures the copper wires and the insulating paper within the stator, preventing potential insulation failure caused by movement between the wires and the insulating paper.

[0004] However, the expandable coating and the insulating paper are prone to separation or cracking, which reduces the electrical and mechanical properties of the expandable insulating film. Summary of the Invention

[0005] In view of the above problems, the embodiments of the present application provide an insulating film and a preparation method, an insulating composite film and a preparation method, and electrical equipment, which can prevent the insulating film from separating or cracking, and improve the electrical and mechanical properties of the insulating film.

[0006] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0007] A first aspect of an embodiment of the present application provides an insulating film comprising a fiber matrix, wherein the fiber matrix comprises an expanded compound fiber matrix.

[0008] In a possible implementation, in terms of mass percentage, the mass percentage of the fiber matrix is ​​70% to 95%, and the mass percentage of the expansion compound is 5% to 30%.

[0009] In a possible implementation, the expansion compound includes a mixture of expansion powder and an organic compound, wherein the mass fraction of the organic compound is 85 to 95 parts, and the mass fraction of the expansion powder is 5 to 15 parts.

[0010] In a possible implementation, the organic compound is formed by a cross-linking reaction between a water-based resin and a modified resin.

[0011] In a possible implementation, the water-based resin includes at least one of acrylic acid, epoxy resin, polyurethane resin, and the like.

[0012] In a possible implementation, the modified resin includes at least one of modified epoxy resin, modified phenolic resin, modified polyvinyl chloride resin, modified polyimide resin, or modified polyetheretherketone resin.

[0013] In a possible implementation, the fiber matrix includes one or more of aramid fiber, polyamide fiber, aramid fiber, and polyester fiber;

[0014] In a possible implementation, the fiber matrix includes one or more of aramid fiber, polyamide fiber, aramid fiber, and polyester fiber;

[0015] Preferably, the fiber matrix includes aramid short fibers and / or aramid fibrids; when the fiber matrix includes the aramid short fibers and the aramid fibrids, the mass ratio of the aramid short fibers to the aramid fibrids is (3-5):(5-7).

[0016] A second aspect of the embodiments of the present application provides an insulating composite membrane, comprising a support membrane and the expandable insulating membrane of the first aspect;

[0017] The expandable insulating membrane is disposed on at least one side of the supporting membrane.

[0018] In a possible implementation manner, the insulating film is connected to both sides of the supporting film through an adhesive layer.

[0019] In a possible implementation, the support film has a thickness of 25 μm to 1000 μm, and / or the adhesive layer has a thickness of 5 μm to 150 μm.

[0020] A third aspect of the embodiments of the present application provides a method for preparing an insulating film, comprising:

[0021] The raw materials including fiber matrix, expansion compound and solvent are mixed to obtain a mixed slurry

[0022] The mixed slurry is subjected to post-treatments including dehydration, cold pressing, drying and calendering in sequence to obtain an insulating film.

[0023] In a possible implementation, a first reaction is performed on a first system including an emulsified modified resin, a water-based resin, an expanding powder, a curing agent, an accelerator, an adhesion promoter, and a defoaming agent to obtain an expanding compound.

[0024] In one possible implementation, a first system consisting of 35 to 50 parts of a modified resin, 35 to 50 parts of a water-based resin, 5 to 15 parts of an expanding powder, 1 to 5 parts of a curing agent, 0 to 3 parts of an accelerator, 1 to 5 parts of an adhesion promoter, and 0 to 3 parts of a defoaming agent, in parts by mass, is mixed and reacted to obtain an expanding compound.

[0025] In one possible implementation, a second system including an aqueous resin, water, and a modifier is subjected to a second reaction to obtain a modified resin;

[0026] The modified resin is emulsified to form an emulsified modified resin.

[0027] In a possible implementation, a third system including a catalyst, an alcoholic hydroxyl monomer, a dihalogenated hydrocarbon monomer, and an organic solvent is subjected to a third reaction to obtain a modifier.

[0028] In a possible implementation, the catalyst, the alcoholic hydroxyl monomer, and the organic solvent are mixed and stirred for a first preset time to obtain a uniformly mixed first mixed liquid;

[0029] mixing the dihalogenated hydrocarbon monomer and the first mixed liquid and stirring them for a second preset time, so that the dihalogenated hydrocarbon monomer and the first mixed liquid react to obtain an initial modifier;

[0030] The initial modifier is allowed to stand at the first preset temperature for a third preset time, and is subjected to precipitation purification to obtain a modifier.

[0031] In one possible implementation, when the fiber matrix includes aramid chopped fibers and aramid fibrids, the method includes:

[0032] Aramid chopped fibers and an intumescent compound are mixed in water and first deflaked using a deflaking machine;

[0033] Then, the aramid fibrid is added to the mixed solution after the first deflaking, and a second deflaking is performed using a deflaking machine to obtain a mixed solution of fiber matrix, swelling compound and water.

[0034] A fourth aspect of the present application provides a method for preparing an insulating composite film, comprising:

[0035] Laminating an insulating film to at least one side of a support film to form a composite film; the insulating film is prepared by the method for preparing an insulating film according to the third aspect;

[0036] The composite film is dried at a third preset temperature and hot-pressed to form an insulating film.

[0037] A fifth aspect of an embodiment of the present application provides an electrical device, comprising the insulating film described in the first aspect, or comprising the insulating composite film described in the second aspect.

[0038] In the insulating film and preparation method, insulating composite film and preparation method, and electrical equipment provided by the embodiments of the present application, the fiber matrix includes an expansion compound, or the expansion compound is directly integrated into the fiber matrix. Thus, the expansion compound creates gaps between the fiber matrix, increasing the expansion space of the insulating film. This allows the insulating film to expand more freely when heated or subjected to other stimuli without being subjected to excessive internal pressure, thereby reducing or even eliminating the risk of cracking. Furthermore, the expansion compound can also increase the toughness of the insulating film, thereby reducing or even eliminating cracking between the expansion compound and the fiber matrix, thereby improving the electrical and mechanical properties of the insulating film.

[0039] In addition to the technical problems solved by the embodiments of the present application described above, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions, other technical problems that can be solved by the insulating film and preparation method, the insulating composite film and preparation method, and the electrical equipment provided by the embodiments of the present application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0041] Figure 1 A schematic structural diagram of an insulating film provided in an embodiment of the present application;

[0042] Figure 2 Schematic diagram of the structure of the modifier provided in the embodiment of this application Figure 1 ;

[0043] Figure 3 Schematic diagram of the structure of the modifier provided in the embodiment of this application Figure 2 ;

[0044] Figure 4 Schematic diagram of the structure of the modifier provided in the embodiment of this application Figure 3 .

[0045] Description of reference numerals:

[0046] 100: insulating film; 200: adhesive layer; 300: supporting film. DETAILED DESCRIPTION

[0047] As described in the background technology, the expandable coating and the insulating paper in the related art are prone to separation or cracking. The inventors have found that the reason for this problem is that the expandable coating is connected to the insulating paper by an adhesive, and the bonding strength between the expandable coating and the insulating paper is poor. When heated or subjected to other stimuli, the expandable coating and the insulating paper are prone to separation or cracking.

[0048] In response to the above-mentioned technical problems, the embodiments of the present application provide an insulating film and a method for preparing the same, an insulating composite film and a method for preparing the same, and an electrical device, wherein the fiber matrix includes an expansion compound, or in other words, the expansion compound is directly integrated into the fiber matrix. Thus, the expansion compound is used to create gaps between the fiber matrix, thereby increasing the expansion space of the insulating film. This allows the insulating film to expand more freely when heated or otherwise stimulated without being subjected to excessive internal pressure, thereby reducing or even avoiding the risk of cracking the insulating film. Furthermore, the expansion compound can also increase the flexibility of the insulating film, reducing or even avoiding the risk of cracking or breaking the expansion compound and the fiber matrix when the insulating film is bent, thereby improving the electrical and mechanical properties of the insulating film.

[0049] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0050] Please refer to the attached Figure 1 The present invention provides an insulating film that can be applied to motors, transformers, and other electrical equipment. For example, the insulating film is applied to a motor stator.

[0051] The insulating film 100 includes a fiber matrix that includes an intumescent compound, or in other words, the intumescent compound is fused into the fiber matrix. Specifically, when preparing the insulating film 100, the fiber matrix and the intumescent compound can be mixed with water to form a mixed slurry. The mixed slurry is then dehydrated or subjected to other operations. This ensures that the resulting insulating film 100 contains both the fiber matrix and the intumescent compound, eliminating the need for an intumescent coating to be applied to the surface of the fiber matrix.

[0052] In this way, there is no obvious connection interface between the expansion compound and the fiber matrix. The expansion compound can also be used to create gaps in the fiber matrix, increasing the expansion space of the insulating film. This allows the insulating film to expand more freely when heated or stimulated by other stimuli, improving the slot fill rate, thereby reducing or even eliminating the risk of cracking of the insulating film. At the same time, the expansion compound can also increase the flexibility of the insulating film, reducing or even eliminating the risk of cracking or breaking between the expansion compound and the fiber matrix when the insulating film is bent, thereby improving the electrical and mechanical properties of the insulating film. The mass percentage of the fiber matrix is ​​70% to 95%, for example, the mass percentage of the fiber matrix is ​​70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 95%, or any two thereof.

[0053] The mass percentage of the expansion compound is 5% to 30%, for example, 5%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or any two thereof, which is beneficial for improving the resistance of the insulating film 100 to breakage or splitting.

[0054] In this embodiment, the amounts of the expansion compound and fiber matrix added can be adjusted based on the desired properties of the insulating film 100. For example, if the insulating film 100 requires greater flexibility, the mass percentage of the expansion compound can be increased. It should be understood that the mass percentage in this embodiment refers to the percentage of the mass of the fiber matrix to the total mass of all materials in the insulating film 100.

[0055] It should be noted that the fiber matrix in this embodiment includes but is not limited to different types of fibers such as aramid fiber, polyamide (POD), polysulfone aramid fiber (PSA), and polyester fiber (PET).

[0056] In the embodiments of the present application, the expandable compound comprises a mixture of expandable powder and an organic compound, wherein the organic compound comprises 85 to 95 parts by weight and the expandable powder comprises 5 to 15 parts by weight. The term "mass fraction" generally refers to the ratio of the mass of a component to the total mass of the mixture. This notation is used to describe the relative amounts of each component in a mixture.

[0057] Among them, an appropriate amount of expansion powder can expand rapidly when heated and fill the gaps in the fiber matrix. On the one hand, the organic compound can play a role in supporting and maintaining structural stability. On the other hand, by adjusting the material of the organic compound, more gaps can be formed in the fiber matrix, thereby providing expansion space. In this way, the expansion powder can be filled into the gaps in the fiber matrix in a timely and effective manner, thereby improving the expansion performance of the insulating film 100.

[0058] This embodiment can also freely set the mass fraction of the organic compound and the mass fraction of the expanding powder based on the performance requirements of the insulating film 100. For example, the insulating film 100 needs to have higher expansion performance, or the insulating film 100 needs to have higher flexibility, thereby improving the design flexibility of the insulating film 100.

[0059] In a possible implementation, the expanded powder includes but is not limited to at least one of polymer shape memory materials, expanded graphite, expanded physical microspheres, expanded microcapsules, and the like.

[0060] It should be noted that the organic compound can be in a variety of forms. In one example, the organic compound can be a water-based resin. The adhesive properties of the water-based resin can enhance the bonding between the expanded powder and the fiber matrix, ensuring that the insulation film maintains stability and reliability during application.

[0061] In another example, the organic compound is formed by a cross-linking reaction between a water-based resin and a modified resin. The modified resin is used to improve the performance of the organic compound. In this embodiment, when preparing the modified resin, the composition and content of the prepared materials can be adjusted to make the modified resin have different groups, thereby making the modified resin have different properties. In one example, please refer to the attached Figure 2 , the modified resin introduces a surface active structure, which significantly improves its hydrophilicity and improves the dispersion of the modified resin in water, so that it can be evenly dispersed during the delamination process, thereby promoting the adhesion of the modified resin to the fiber matrix. In another example, please refer to the attached Figure 3 The rigid structure of the benzene rings at both ends of the modified resin chain allows gaps between the molecular chains and the fiber matrix, leaving room for subsequent expansion. In another example, the addition of long chain structures to the modified resin molecules gives the modified resin a certain degree of flexibility. After curing, it is not brittle and can be bent and used in practice without cracking the surface.

[0062] The synergistic effect of the water-based resin and the modified resin enables the organic compound to have both the properties of the water-based resin and the properties of the modified resin. For example, the organic compound has both the rigidity of the water-based resin and the flexibility of the modified resin.

[0063] In a possible implementation, when the fiber matrix is ​​aramid fiber, the fiber matrix may include aramid short fibers and / or aramid fibrids. In one example, the fiber matrix includes aramid short fibers, or the fiber matrix includes aramid fibrids.

[0064] In another example, the fiber matrix includes aramid short fibers and aramid fibrids, wherein the mass ratio of the aramid short fibers to the aramid fibrids is (3-5):(5-7). For example, the mass ratio of the aramid short fibers to the aramid fibrids includes, but is not limited to, 3:7, 4:6, and 5:5.

[0065] In this way, the aramid chopped fibers enhance the mechanical strength of the fiber matrix. These chopped fibers form an effective reinforcement network within the matrix, resisting external forces such as stretching, compression, and bending, thereby improving the structural stability and durability of the entire insulating film. Furthermore, the aramid fibrids enhance the dielectric strength of the fiber matrix. By rationally setting the mass ratio of aramid chopped fibers to aramid fibrids, this embodiment effectively achieves a good balance between mechanical and dielectric strength in the insulating film.

[0066] In addition, it is also beneficial to optimize the arrangement and distribution of the fibers, so that when mixed with the expansion compound to prepare the insulating film 100, the expansion compound can better penetrate and fill the gaps in the fiber matrix, thereby improving the insulating film 100's ability to resist cracking and breaking.

[0067] An embodiment of the present application also provides an insulating composite film, including a support film 300 and the insulating film 100 described in any of the above embodiments, wherein the support film 300 is used to provide mechanical support for the insulating film 100, wherein the material of the support film 300 includes but is not limited to polyimide film, polyester film, etc.

[0068] The insulating film 100 is disposed on at least one side of the support film 300. For example, the insulating film 100 has one layer, and the insulating film 100 is disposed on one side of the support film 300. For another example, the insulating film 100 has two layers, and the two insulating films 100 are disposed on both sides of the support film 300, respectively.

[0069] The insulating film 100 can be directly laminated on the support film 300, and the connection between the insulating layer 100 and the support film 300 can be achieved by lamination. The insulating film 100 can also be provided on the support film 300 by other connection methods. For example, the insulating film 100 is provided on at least one side of the support film 300 via the adhesive layer 200.

[0070] It should be understood that when the insulating film 100 has two layers, the insulating film 100 is connected to both sides of the support film 300 via the adhesive layer 200, so that the insulating composite film has a five-layer structure. The adhesive layer 200 may be made of, but is not limited to, epoxy adhesive, acrylic resin adhesive, polyurethane adhesive, and the like.

[0071] Since the insulating composite film provided in this embodiment includes the insulating film 100 described in any of the above embodiments, the insulating composite film has all the structures and beneficial effects of the insulating film 100 , which will not be described in detail in this embodiment.

[0072] In order to control the thickness of the insulating composite film, this embodiment also limits the thickness of the support film 300 and / or the adhesive layer 200. Exemplarily, the thickness of the support film 300 is 25 μm to 1000 μm. In one example, the thickness of the support film 300 is 25 μm, 50 μm, 52 μm, 55 μm, 58 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, and a range between any two values.

[0073] And / or, the thickness of the adhesive layer 200 is 5 μm to 150 μm. In one example, the thickness of the adhesive layer 200 is 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or a range between any two values.

[0074] This embodiment, by rationally setting the thickness of the support film 300 and the adhesive layer 200, ensures the structural strength of the insulating composite film while maintaining a moderately thick film, thereby reducing the risk of the insulating composite film breaking during bending. Furthermore, the support film 300 can also improve the electrical insulation performance of the insulating composite film.

[0075] An embodiment of the present application provides an electrical device, comprising the insulating film described in any of the above embodiments, or comprising the insulating composite film described in any of the above embodiments.

[0076] Since the insulating film or insulating composite film reduces or even avoids the risk of delamination or cracking during use, the overall structural stability of the electrical equipment is significantly improved, which helps to extend the service life of the electrical equipment and reduce the failure rate caused by material failure.

[0077] An embodiment of the present application also provides a method for preparing an insulating film, where the insulating film is the insulating film described in any of the above embodiments.

[0078] The method for preparing the insulating film comprises the following steps:

[0079] Raw materials including a fiber matrix, an expansion compound, and a solvent are mixed to obtain a mixed slurry. For example, the fiber matrix and the expansion compound in a certain mass ratio can be fully mixed in water and deflaked using a deflaker to obtain a mixed slurry of the fiber matrix, the expansion compound, and water.

[0080] Afterwards, the mixed slurry is subjected to post-treatments including dehydration, cold pressing, drying and calendering in sequence to obtain an insulating film.

[0081] Exemplarily, a mixture of the fiber matrix, the expansion compound and water is poured into a paper sheet former with an inner diameter of 200 mm to obtain a wet sheet after dehydration; the wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0082] In the above-mentioned preparation process, the expansion compound, the fiber matrix and water are directly and evenly mixed, and then the mixture is dehydrated or subjected to other operations to obtain the insulating film 100 described in any of the above-mentioned embodiments. In other words, the prepared insulating film 100 contains both the fiber matrix and the expansion compound, and there is no need to adhere the expansion coating to the surface of the fiber matrix in the form of coating.

[0083] This eliminates a distinct interface between the expansion compound and the fiber matrix. Furthermore, the expansion compound creates gaps within the fiber matrix, increasing the space for expansion of the insulating film. This allows the film to expand more freely when exposed to heat or other stimuli, improving the slot fill rate and reducing or even eliminating the risk of cracking. Furthermore, the expansion compound enhances the film's flexibility, reducing or even eliminating the risk of cracking or breaking between the expansion compound and the fiber matrix when the film is bent, thereby improving the film's electrical and mechanical properties.

[0084] It should be understood that the fiber matrix used in this embodiment can be a single type of aramid fiber, or two or even more types of aramid fibers.

[0085] Exemplarily, when the fiber matrix comprises aramid short fibers and aramid fibrids, the mixing process of the fiber matrix and the swelling compound comprises the following steps:

[0086] Aramid chopped fibers and an intumescent compound are mixed in water and a first deflaking is performed using a deflaking machine.

[0087] Then, the aramid fibrid is added to the mixed solution after the first deflaking, and a second deflaking is performed using a deflaking machine to obtain a mixed solution of fiber matrix, swelling compound and water.

[0088] It should be understood that the structure and working process of the deflaking machine are in the related art and will not be described in detail in this embodiment.

[0089] In one possible implementation, the process of preparing the expansion compound may include the following steps:

[0090] A first reaction is performed on a first system including an organic compound, an expanding powder, a curing agent, an accelerator, an adhesion promoter and a defoaming agent to obtain an expanding compound.

[0091] Illustratively, when the organic compound includes a modified resin and an aqueous resin, the method for preparing an expansion compound further includes: adding a first system formed by, in parts by mass, 35 to 50 parts of a modified resin, 35 to 50 parts of an aqueous resin, 5 to 15 parts of an expansion powder, 1 to 5 parts of a curing agent, 0 to 3 parts of an accelerator, 1 to 5 parts of an adhesion promoter, and 0 to 3 parts of a defoaming agent into a reactor, dispersing the system at high speed, and causing a first reaction to obtain an expansion compound.

[0092] Among them, the first reaction can include a reaction between a modified resin and a water-based resin. For example, the modified resin has an active group that can react with certain groups of the water-based resin. Under certain conditions, the modified resin and the water-based resin can react with each other to form a substance with a cross-linked network structure.

[0093] In this embodiment, an accelerator is also added, which can accelerate the reaction between the modified resin and the water-based resin.

[0094] The first reaction also includes a bonding reaction between the expanding powder and the substance having a cross-linked network structure, and the adhesion promoter can promote the expanding powder to quickly adhere to the substance having a cross-linked network structure to form an expanding compound.

[0095] It should be noted that the functions of the curing agent and the defoaming agent are prior art and will not be elaborated in this embodiment.

[0096] In this embodiment, the water-based resin includes at least one of acrylic acid, epoxy resin, polyurethane resin, etc. When the water-based resin includes a mixture of epoxy resin and polyurethane resin, the mass ratio of epoxy resin to polyurethane resin is 6:4, which can improve the flexibility of the water-based resin.

[0097] The modified resin includes at least one of a modified epoxy resin, a modified phenolic resin, a modified polyvinyl chloride resin, a modified polyimide resin, or a modified polyetheretherketone resin. When the modified resin includes a mixture of a modified epoxy resin and a modified polyimide resin, and the mass ratio of the modified epoxy resin to the modified polyimide resin is 9:1, the flexibility of the modified resin can be improved.

[0098] The preparation process of the modified resin can refer to the following steps:

[0099] The second system including the water-based resin, water and the modifier is subjected to a second reaction to obtain a modified resin.

[0100] Illustratively, the aqueous resin, water, and the modifier are mixed in a certain mass ratio and reacted at a second preset temperature for a fourth preset time to form the modified resin.

[0101] The second preset temperature is 80-85° C., and the fourth preset time is 2.5-3 hours. Water-based resins include but are not limited to acrylic resins, epoxy resins, and polyurethane resins.

[0102] It should be noted that the second reaction includes a reaction between the water-based resin and the modifier, so that the water-based resin has certain specific groups.

[0103] Thereafter, the modified resin is emulsified to form an emulsified modified resin.

[0104] For example, the modified resin is neutralized with a sodium hydroxide aqueous solution and emulsified with a high shear dispersing emulsifier to form an emulsified modified resin.

[0105] In this embodiment, by preparing the modified resin into an emulsified state, it is not necessary to add additional water solvent when mixing the first system including the emulsified modified resin, water-based resin, expansion powder, curing agent, accelerator, adhesion promoter and defoaming agent.

[0106] In one possible implementation, a third system comprising a catalyst, an alcoholic hydroxyl monomer, a dihalogenated hydrocarbon monomer, and an organic solvent is subjected to a third reaction to obtain the modifier, wherein the third reaction may comprise a reaction between the alcoholic hydroxyl monomer and the dihalogenated hydrocarbon monomer.

[0107] It should be noted that, in specific operations, the reactants mentioned above can be directly placed into the reaction chamber, or other methods can be used.

[0108] Exemplarily, the catalyst, alcoholic hydroxyl monomer and organic solvent are stirred and mixed, and stirred for a first preset time to form a first mixed liquid; wherein the first preset time is 0.5h to 1.5h, and exemplarily, the first preset time is 1h.

[0109] Subsequently, the dihalogenated hydrocarbon monomer is added to the first mixed solution and stirred for a second predetermined time to form a second mixed solution; wherein the second predetermined time is 5 hours to 8 hours. It should be understood that the reaction temperature at this stage can also be controlled, for example, the reaction temperature is 75°C to 85°C, and illustratively, the reaction temperature is 80°C.

[0110] Then, the second mixed liquid is diluted with water and ethanol and precipitated, and allowed to stand at a first preset temperature for a third preset time to form a modifier. The first preset temperature is 65° C. to 75° C., and illustratively, the first preset temperature is 70° C.

[0111] Among them, the alcohol hydroxyl monomer includes but is not limited to at least one of a monomer containing a benzene ring structure or its derivatives, a monomer containing a naphthalene structure or its derivatives, a monomer containing a biphenyl structure or its derivatives, a monomer containing a double bond structure or its derivatives, a monomer containing a triple bond structure or its derivatives, a monomer containing a tri-condensed ring structure or its derivatives, a monomer containing a pyridine ring, an imidazole ring, an oxazole ring, a thiazole ring, a pyrimidine ring or a triazine ring heterocyclic structure, etc.

[0112] The dihalogenated hydrocarbon monomers include but are not limited to at least one of hydroxyl-containing monomers or derivatives thereof, amino-containing monomers or derivatives thereof, quaternary ammonium-containing monomers or derivatives thereof, ether-containing monomers or derivatives thereof, carboxyl-containing monomers or derivatives thereof, amide-containing monomers or derivatives thereof, and the like.

[0113] The organic solvent includes but is not limited to at least one of dimethylformamide, dimethyl sulfoxide, acetone, acetonitrile, dimethylacetamide, sulfolane, ether, tetrahydrofuran, methyl ethyl ketone and the like.

[0114] The present application also provides a method for preparing an insulating composite film, which further includes:

[0115] The insulating film is laminated to at least one side of the support film to form a composite film. For example, an adhesive is evenly applied to the surface of the insulating film using a coating machine to obtain an adhesive-coated insulating film.

[0116] Then, the insulating film coated with an adhesive is attached to at least one surface of the support film to obtain a composite film.

[0117] The composite film is then dried at a third predetermined temperature and hot-pressed to form an insulating film. For example, the composite film is dried in a dryer at 80°C for 10 minutes and then hot-pressed at 105°C and a pressure of 10 MPa for 5 minutes to form an insulating film.

[0118] The present application is further described below through specific examples. In the following examples and comparative examples, laboratory hand sheets are used as examples. The hand sheets are circles with a diameter of 200 mm and an area of ​​0.0314 m2.

[0119] Example 1

[0120] Preparation of modifier:

[0121] At room temperature, 41.46 g of potassium carbonate, 36.52 g of methyl parahydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38 ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier.

[0122] Preparation of emulsified modified resin:

[0123] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 2 .

[0124] Prepare the intumescent compound:

[0125] The weight fraction of the organic compound is 90 parts, and the weight fraction of the expanding powder is 10 parts. Specifically, 40g of water-based bisphenol A epoxy resin, 40g of modified epoxy emulsion, 10g of expanding physical microspheres, 5g of an amine curing agent, 0.5g of an imidazole accelerator, 1g of a silane coupling agent, and 0.6g of a silicone defoamer are added to a reaction kettle. After high-speed dispersion, vacuum degassing is performed to obtain the expanding compound.

[0126] Preparation of insulating film:

[0127] The mass percentage of the fiber matrix is ​​95%, and the mass percentage of the expanded compound is 5%; specifically, 14.5g of aramid short fibers and 2.5g of the compound are mixed in water and then deflagred with a deflagrator, and then 33g of aramid precipitated fibers are added for secondary deflagration; the mixture is then stirred to obtain a mixture, and the mixture is poured into a paper sheet former with an inner diameter of 200mm, and dehydrated to obtain a wet sheet; the wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0128] Preparation of insulating composite film:

[0129] The adhesive was evenly applied to the surface of the insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; the insulating film-support film-insulating film were laminated in the order of lamination to obtain a composite film; the composite film was dried in a dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0130] Experimental Example 2

[0131] Preparation of modifier:

[0132] At room temperature, 41.46g of potassium carbonate, 36.52g of methyl parahydroxybenzoate and 250ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction, the solution was cooled to room temperature and then reprecipitated with water and ethanol in sequence. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier. 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier were added to a three-necked flask and reacted at 80-85°C for 3 hours to obtain a modified epoxy resin. The obtained modified epoxy resin was first neutralized with an aqueous sodium hydroxide solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with a structure such as Figure 2 .

[0133] Prepare the intumescent compound:

[0134] The weight fraction of the organic compound is 90 parts, and the weight fraction of the expanding powder is 10 parts. Specifically, 40g of waterborne bisphenol A epoxy resin, 40g of modified epoxy emulsion, 10g of expanding physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, and 0.6g of silicone defoamer are added to a reaction kettle. After high-speed dispersion, vacuum degassing is performed to obtain the expanding compound.

[0135] The mass percentage of the fiber matrix is ​​92%, and the mass percentage of the expanding compound is 8%; specifically, 13.8g of aramid short fibers and 4g of the expanding compound are mixed in water and then deflagred using a deflagrator, and then 32.2g of aramid precipitated fibers are added for secondary deflagration; the mixture is then stirred to obtain a mixture, and the mixture is poured into a paper sheet former with an inner diameter of 200mm, and dehydrated to obtain a wet sheet; the wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0136] Preparation of insulating composite film

[0137] An adhesive is evenly applied to the surface of an insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; a composite film is obtained by laminating the insulating film-support film-insulating film in the order of insulating film-support film-insulating film; the composite film is dried in a paper dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0138] Experimental Example 3

[0139] Preparation of modifier:

[0140] At room temperature, 41.46 g of potassium carbonate, 36.52 g of methyl parahydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38 ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier.

[0141] Preparation of emulsified modified resin:

[0142] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 2 .

[0143] Prepare the intumescent compound:

[0144] The weight fraction of the organic compound is 90 parts, and the weight fraction of the expanding powder is 10 parts. Specifically, 40g of waterborne bisphenol A epoxy resin, 40g of modified epoxy emulsion, 10g of expanding physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, and 0.6g of silicone defoamer are added to a reaction kettle. After high-speed dispersion, vacuum degassing is performed to obtain the expanding compound.

[0145] Preparation of insulating film:

[0146] The mass percentage of the fiber matrix is ​​88%, and the mass percentage of the expanding compound is 12%; specifically, 13.2g of aramid chopped fibers and 6g of the expanding compound are mixed in water and then deflagred using a deflagrator, and then 30.8g of aramid precipitated fibers are added for secondary deflagration; the mixture is then stirred to obtain a mixture, and the mixture is poured into a paper sheet former with an inner diameter of 200mm, and dehydrated to obtain a wet sheet; the wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0147] Preparation of insulating composite film:

[0148] An adhesive is evenly applied to the surface of an insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; a composite film is obtained by laminating the insulating film-support film-insulating film in the order of insulating film-support film-insulating film; the composite film is dried in a paper dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0149] Experimental Example 4

[0150] Preparation of modifier:

[0151] At room temperature, 41.46 g of potassium carbonate, 36.52 g of methyl parahydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38 ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier.

[0152] Preparation of emulsified modified resin:

[0153] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 2 .

[0154] Prepare the intumescent compound:

[0155] The mass fraction of the organic compound is 90 parts, and the mass fraction of the expanding powder is 10 parts. Specifically, 40g of waterborne bisphenol A epoxy resin, 40g of modified epoxy emulsion, 10g of expanding physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, and 0.6g of silicone defoamer are added to a reaction kettle. After high-speed dispersion, vacuum degassing is performed to obtain the modified expanding compound.

[0156] Preparation of insulating film:

[0157] The mass percentage of the fiber matrix is ​​84%, and the mass percentage of the expanding compound is 16%. Specifically, 12.6 g of aramid short fibers and 8 g of the modified expanding compound are mixed in water and then deflated using a deflagrator, and then 29.4 g of aramid precipitated fibers are added for secondary deflagration. The mixture is then stirred to obtain a mixture, which is poured into a paper sheet former with an inner diameter of 200 mm and dehydrated to obtain a wet sheet. The wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0158] Preparation of insulating composite film:

[0159] The adhesive was evenly applied to the surface of the insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; the insulating film-support film-insulating film were laminated in the order of lamination to obtain a composite film; the composite film was dried in a dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0160] Example 5

[0161] At room temperature, 41.46 g of potassium carbonate, 36.52 g of methyl parahydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38 ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier.

[0162] Preparation of emulsified modified resin:

[0163] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 2 .

[0164] Prepare the intumescent compound:

[0165] The mass fraction of the organic compound is 88 parts, and the mass fraction of the expanding powder is 12 parts. Specifically, 50g of waterborne bisphenol A epoxy resin, 60g of modified epoxy emulsion, 15g of expanding physical microspheres, 6g of amine curing agent, 1.5g of imidazole accelerator, 5g of silane coupling agent, and 2g of silicone defoamer are added to a reaction kettle. After high-speed dispersion, vacuum degassing is performed to obtain the expanding compound.

[0166] Preparation of insulating film:

[0167] The mass percentage of the fiber matrix is ​​84%, and the mass percentage of the expanding compound is 16%; specifically, 12.6g of aramid short fibers and 8g of the expanding compound are mixed in water and then deflagred using a deflagrator, and then 29.4g of aramid precipitated fibers are added for secondary deflagration; the mixture is then stirred to obtain a mixture, and the mixture is poured into a paper sheet former with an inner diameter of 200mm, and dehydrated to obtain a wet sheet; the wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0168] Preparation of insulating composite film:

[0169] An adhesive is evenly applied to the surface of an insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; a composite film is obtained by laminating the insulating film-support film-insulating film in the order of insulating film-support film-insulating film; the composite film is dried in a paper dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0170] Experimental Example 6

[0171] Preparation of modifier:

[0172] At room temperature, 41.46 g of potassium carbonate, 39.88 g of ethyl p-hydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38 ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to produce an epoxy modifier.

[0173] Preparation of emulsified modified resin:

[0174] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 3 .

[0175] Prepare the intumescent compound:

[0176] The weight fraction of the organic compound is 91 parts, and the weight fraction of the expanding powder is 9 parts. Specifically, 48g of waterborne bisphenol A epoxy resin, 62g of modified epoxy emulsion, 12g of expanding physical microspheres, 3.3g of amine curing agent, 2g of imidazole accelerator, 2.5g of silane coupling agent, and 1.6g of silicone defoamer were added to a reaction kettle. After high-speed dispersion, vacuum degassing was performed to obtain the expanding compound.

[0177] Preparation of insulating film:

[0178] The mass percentage of the fiber matrix is ​​84%, and the mass percentage of the expanding compound is 16%; specifically, 12.6g of aramid short fibers and 8g of the expanding compound are mixed in water and then deflagred using a deflagrator, and then 29.4g of aramid precipitated fibers are added for secondary deflagration; the mixture is then stirred to obtain a mixture, and the mixture is poured into a paper sheet former with an inner diameter of 200mm, and dehydrated to obtain a wet sheet; the wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0179] Preparation of insulating composite film:

[0180] An adhesive is evenly applied to the surface of an insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; a composite film is obtained by laminating the insulating film-support film-insulating film in the order of insulating film-support film-insulating film; the composite film is dried in a paper dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0181] Experimental Example 7

[0182] Preparation of modifier:

[0183] At room temperature, 41.46 g of potassium carbonate, 36.52 g of methyl parahydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 45.35 g of hydroxyethylene glycol halochloride was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier.

[0184] Preparation of emulsified modified resin:

[0185] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 4 .

[0186] Prepare the intumescent compound:

[0187] The mass fraction of the organic compound is 94 parts, and the mass fraction of the expanding powder is 6 parts. Specifically, 45g of waterborne bisphenol A epoxy resin, 65g of modified epoxy emulsion, 8g of expanding physical microspheres, 4g of amine curing agent, 1.2g of imidazole accelerator, 3g of silane coupling agent, and 1.3g of silicone defoamer were added to a reaction kettle. After high-speed dispersion, vacuum degassing was performed to obtain the expanding compound.

[0188] Preparation of insulating film:

[0189] The mass percentage of the fiber matrix is ​​84%, and the mass percentage of the expanding compound is 16%; specifically, 12.6g of aramid short fibers and 8g of the expanding compound are mixed in water and then deflagred using a deflagrator, and then 29.4g of aramid precipitated fibers are added for secondary deflagration; the mixture is then stirred to obtain a mixture, and the mixture is poured into a paper sheet former with an inner diameter of 200mm, and dehydrated to obtain a wet sheet; the wet sheet is subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0190] Preparation of insulating composite film:

[0191] An adhesive is evenly applied to the surface of an insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; a composite film is obtained by laminating the insulating film-support film-insulating film in the order of insulating film-support film-insulating film; the composite film is dried in a paper dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0192] Example 8

[0193] This embodiment differs from embodiment 7 in that the mass percentages of the expansion compound and the fiber matrix are different. For example, the mass percentage of the fiber matrix is ​​70%, and the mass percentage of the expansion compound is 30%.

[0194] Example 9

[0195] This example differs from Example 1 in the composition of the intumescent compound. For example, the fiber matrix comprises 95% by weight of the intumescent compound, which comprises 5% by weight. The intumescent compound includes intumescent powder and a water-based resin. In other words, compared to Example 1, the intumescent compound in this example is unmodified.

[0196] Example 10

[0197] This example differs from Example 4 in the composition of the intumescent compound. For example, the fiber matrix accounts for 84% by mass, while the intumescent compound accounts for 16% by mass. The intumescent compound includes intumescent powder and a water-based resin. In other words, compared to Example 4, the intumescent compound in this example is unmodified.

[0198] Specifically, the intumescent compound is a waterborne bisphenol A epoxy resin.

[0199] Preparation of intumescent compounds

[0200] Add 80g of water-based bisphenol A epoxy resin, 10g of expandable physical microspheres, 5g of an amine curing agent, 0.5g of an imidazole accelerator, 1g of a silane coupling agent, and 0.6g of an organosilicon defoamer to a reactor. After high-speed dispersion, vacuum degassing is performed to obtain an expandable compound.

[0201] Preparation of insulating film

[0202] 12.6 g of aramid chopped fibers and 8 g of an expanding compound were mixed in water and deflurred using a deflurring machine, followed by the addition of 29.4 g of aramid fibrils. The mixture was then stirred to obtain a mixture, which was poured into a paper sheet former with an inner diameter of 200 mm and dehydrated to obtain a wet sheet. The wet sheet was subjected to a flat-plate cold press for 5 minutes, and then transferred to a paper sheet dryer, dried at 80° C. for 10 minutes, and subjected to low-temperature calendering at 105° C. to obtain an insulating film.

[0203] Preparation of insulating composite film

[0204] An adhesive is evenly applied to the surface of an insulating film using a coater to obtain an insulating film coated with the adhesive, with a coating thickness of 30 μm; a composite film is obtained by laminating the insulating film-support film-insulating film in the order of insulating film-support film-insulating film; the composite film is dried in a paper dryer at 80° C. for 10 minutes, and then hot-pressed at 105° C. and a pressure of 10 MPa for 5 minutes to obtain an insulating composite film.

[0205] Example 11

[0206] This example differs from Example 8 in the composition of the intumescent compound. For example, the fiber matrix accounts for 70% by mass and the intumescent compound accounts for 30% by mass. The intumescent compound comprises intumescent powder and a water-based resin. In other words, compared to Example 8, the intumescent compound in this example is unmodified.

[0207] Comparative Example 1

[0208] Compared with the examples, this comparative example coated the expansion compound on the surface of the insulating film.

[0209] Preparation of modifier:

[0210] At room temperature, 41.46 g of potassium carbonate, 36.52 g of methyl parahydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38 ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier.

[0211] Preparation of emulsified modified resin:

[0212] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 1 .

[0213] Preparation of modified intumescent compounds:

[0214] Add 40g of water-based bisphenol A epoxy resin, 40g of modified epoxy emulsion, 10g of expandable physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, and 0.6g of silicone defoamer to a reactor. After high-speed dispersion, vacuum degassing is performed to obtain an expandable compound.

[0215] Preparation of insulating composite film:

[0216] 15 g of aramid short fibers were mixed in water and then deflurred using a deflurring machine, and then 35 g of aramid precipitated fibers were added for secondary deflurring; the mixture was then stirred to obtain a mixture, which was poured into a paper sheet former with an inner diameter of 200 mm and dehydrated to obtain a wet sheet; the wet sheet was subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0217] An adhesive was evenly applied to the surface of the insulating film using a coater to obtain an adhesive-coated insulating film with a coating thickness of 30 μm. The insulating film, support film, and insulating film were laminated in the order of insulation film, support film, and insulation film to obtain a composite film. The composite film was dried in a paper dryer at 80°C for 10 minutes and then hot-pressed at 105°C and a pressure of 10 MPa for 5 minutes. An intumescent compound was evenly applied to the surface of the composite film using a coater and then dried in a paper dryer at 60°C for 10 minutes to obtain an insulating composite film.

[0218] Comparative Example 2

[0219] Compared with the examples, this comparative example adds an expansion compound to the adhesive to cause the adhesive layer to expand.

[0220] Preparation of modifier:

[0221] At room temperature, 41.46 g of potassium carbonate, 36.52 g of methyl parahydroxybenzoate, and 250 ml of dimethylformamide (DMF) were added to a round-bottom flask and stirred for 1 hour. 15.38 ml of 2-bromoethyl methyl ether was added. The reaction mixture was stirred at 80°C overnight. After the reaction was completed, the solution was cooled to room temperature and then reprecipitated with water and then ethanol. The resulting product was vacuum dried at 70°C overnight to obtain an epoxy modifier.

[0222] Preparation of emulsified modified resin:

[0223] Add 50g of E-44 epoxy resin, 300ml of water and 87.4g of epoxy modifier into a three-necked flask and react at 80-85℃ for 3 hours to obtain modified epoxy resin. The obtained modified epoxy resin is first neutralized with sodium hydroxide aqueous solution and then emulsified with a high shear dispersing emulsifier to obtain a stable modified epoxy emulsion with the structure shown in FIG. Figure 1 .

[0224] Preparation of modified intumescent compounds:

[0225] Add 40g of water-based bisphenol A epoxy resin, 40g of modified epoxy emulsion, 10g of expandable physical microspheres, 5g of amine curing agent, 0.5g of imidazole accelerator, 1g of silane coupling agent, and 0.6g of silicone defoamer to a reactor. After high-speed dispersion, vacuum degassing is performed to obtain an expandable compound.

[0226] Preparation of insulating composite film:

[0227] 15 g of aramid short fibers were mixed in water and then deflurred using a deflurring machine, and then 35 g of aramid precipitated fibers were added for secondary deflurring; the mixture was then stirred to obtain a mixture, which was poured into a paper sheet former with an inner diameter of 200 mm and dehydrated to obtain a wet sheet; the wet sheet was subjected to flat-plate cold pressing for 5 minutes, and then transferred to a paper sheet dryer, dried at 80°C for 10 minutes, and subjected to low-temperature calendering at 105°C to obtain an insulating film.

[0228] The mixed adhesive and intumescent compound were evenly applied to the surface of the insulating film using a coater to produce an insulating composite film coated with intumescent adhesive to a thickness of 30 μm. The insulating film, support film, and insulating film were laminated in the order of insulation film, support film, and insulation film to produce the insulating composite film. The insulating composite film was dried in a paper dryer at 80°C for 10 minutes and then hot-pressed at 105°C and 10 MPa for 5 minutes. The intumescent compound was evenly applied to the surface of the composite film using a coater to a thickness of 15 μm. The composite film was then dried in a paper dryer at 60°C for 10 minutes to produce the insulating composite film.

[0229] This embodiment performs an expansion ratio test, a breakdown voltage test, and a bending test on the insulating films formed in the above embodiments and comparative examples. The relevant standards of each test are as follows:

[0230] Expansion ratio test

[0231] The insulating film is heated to 170°C. The dimensions of the expandable insulating paper before and after expansion in the thickness direction are measured. The expansion ratio is calculated using the following formula: Expansion ratio = thickness after expansion / thickness before expansion.

[0232] Breakdown voltage test

[0233] GB / T 1408.1-2016 is used to test the breakdown voltage of insulating materials.

[0234] Bending test

[0235] The insulating film is heated to 170°C to expand. The sample is bent before and after expansion to observe whether the sample has cracks or delamination.

[0236] Table 1 Data of expansion ratio, breakdown voltage test and bending test of the embodiment and comparative example

[0237]

[0238] It can be seen from the above table that with the addition of expansion compound, the expansion ratio gradually increases, and the expansion compound has no effect on the breakdown voltage.

[0239] The data from Examples 9-11 in the table above also shows that when the intumescent compound does not contain a modified resin, the expansion ratio is significantly lower than that of Experiments 1-8, which incorporate a modified epoxy resin, at the same dosage. This is because the smaller interstices within the fiber matrix prevent the intumescent microspheres from fully expanding under heating. Therefore, the modified epoxy resin effectively increases the expansion ratio of the insulating film, thereby fully securing the insulating composite film and enameled wire and improving the slot fill ratio.

[0240] It can also be seen from the data of Examples 4 to 7 in the above table that, under the premise of the same amount of fiber matrix added, the expansion ratio gradually increases with the increase in the number of expanding powders, and the expanding compound has no effect on the breakdown voltage.

[0241] The table above also shows that when the intumescent compound is applied to the fiber substrate or adhesive layer, cracks, delamination, and even bulging occur after expansion and bending. The various embodiments or implementations in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between the various embodiments can be referenced separately.

[0242] It should be noted that references in this specification to "one embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not necessarily every embodiment includes that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not.

[0243] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An insulating film, characterized in that: A fibrous matrix is ​​included that includes an intumescent compound.

2. The insulating film according to claim 1, wherein In terms of mass percentage, the mass percentage of the fiber matrix is ​​70% to 95%, and the mass percentage of the expansion compound is 5% to 30%.

3. The insulating film according to claim 1, wherein The expansion compound comprises a mixture of expansion powder and an organic compound, wherein the mass fraction of the organic compound is 85 to 95 parts, and the mass fraction of the expansion powder is 5 to 15 parts.

4. The insulating film according to claim 3, wherein The organic compound is formed by a cross-linking reaction between a water-based resin and a modified resin.

5. The insulating film according to claim 4, wherein The water-based resin includes at least one of acrylic acid, epoxy resin, polyurethane resin, etc.

6. The insulating film according to claim 5, wherein The modified resin includes at least one of modified epoxy resin, modified phenolic resin, modified polyvinyl chloride resin, modified polyimide resin or modified polyetheretherketone resin.

7. The insulating film according to any one of claims 1 to 6, characterized in that: The fiber matrix includes one or more of aramid fiber, polyamide fiber, aramid sulfone fiber, and polyester fiber; Preferably, the fiber matrix includes aramid short fibers and / or aramid fibrids; when the fiber matrix includes the aramid short fibers and the aramid fibrids, the mass ratio of the aramid short fibers to the aramid fibrids is (3-5):(5-7).

8. An insulating composite film, characterized in that: comprising a support film and the insulating film according to any one of claims 1 to 7; The insulating film is disposed on at least one side of the supporting film.

9. The insulating composite film according to claim 8, characterized in that: The insulating film is connected to opposite sides of the supporting film through an adhesive layer.

10. The insulating composite film according to claim 9, characterized in that: The thickness of the support film is 25 μm to 1000 μm, and / or the thickness of the adhesive layer is 5 μm to 150 μm.

11. A method for preparing an insulating film according to any one of claims 1 to 10, characterized in that: The following steps are involved: Mixing raw materials including a fiber matrix, an expansion compound, and a solvent to obtain a mixed slurry; The mixed slurry is subjected to post-treatments including dehydration, cold pressing, drying and calendering in sequence to obtain an insulating film.

12. The method for preparing an insulating film according to claim 11, wherein: A first reaction is performed on a first system including an organic compound, an expanding powder, a curing agent, an accelerator, an adhesion promoter and a defoaming agent to obtain an expanding compound.

13. The method for preparing an insulating film according to claim 12, wherein: The organic compound includes a modified resin and a water-based resin; A first system formed by, in parts by mass, 35 to 50 parts of a modified resin, 35 to 50 parts of a water-based resin, 5 to 15 parts of an expanding powder, 1 to 5 parts of a curing agent, 0 to 3 parts of an accelerator, 1 to 5 parts of an adhesion promoter, and 0 to 3 parts of a defoaming agent is mixed and reacted to obtain an expanding compound.

14. The method for preparing an insulating film according to any one of claims 11 to 13, characterized in that: performing a second reaction on a second system including a water-based resin, water and a modifier to obtain a modified resin; The modified resin is emulsified to form an emulsified modified resin.

15. The method for preparing an insulating film according to claim 14, wherein: A third system including a catalyst, an alcoholic hydroxyl monomer, a dihalogenated hydrocarbon monomer and an organic solvent is subjected to a third reaction to obtain a modifier.

16. The method for preparing an insulating film according to claim 15, wherein: Mixing the catalyst, the alcoholic hydroxyl monomer, and the organic solvent, and stirring for a first preset time to obtain a uniformly mixed first mixed liquid; mixing the dihalogenated hydrocarbon monomer and the first mixed liquid and stirring them for a second preset time, so that the dihalogenated hydrocarbon monomer and the first mixed liquid react to obtain an initial modifier; The initial modifier is allowed to stand at the first preset temperature for a third preset time, and is subjected to precipitation purification to obtain the modifier.

17. The method for preparing an insulating film according to any one of claims 11 to 13, characterized in that: When the fiber matrix comprises aramid short fibers and aramid fibrids, the method comprises: Aramid chopped fibers and an intumescent compound are mixed in water and first deflaked using a deflaking machine; Then, the aramid fibrid is added to the mixed solution after the first deflaking, and a second deflaking is performed using a deflaking machine to obtain a mixed solution of fiber matrix, swelling compound and water.

18. A method for preparing an insulating composite film, characterized in that: include: Laminating an insulating film to at least one side of a support film to form a composite film; the insulating film is prepared by the method for preparing an insulating film according to any one of claims 11 to 17; The composite film is dried at a third preset temperature and hot-pressed to form an insulating film.

19. An electrical device, characterized in that: The insulating film comprises the insulating film according to any one of claims 1 to 7, or the insulating composite film according to any one of claims 8 to 10.

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